Conversion of propylene polymers



June 1952 L. F. BROOKE CONVERSION OF PROPYLENE POLYMERS 3 Sheets-Sheet 1 Filed June 4, 1949 H 0: m w fi mm EN mm m w mv m Mi w H H 3 \mP d H H l. O M 1% m #1 m T m mm M S d 8 3 m m n m w m 9 V Z s m w n n m om 2 w 8 a N M mv m ml BYI June 10, 1952 L. F. BROOKE Filed June 4. 1949 3 Sheets-Sheet 2 F-12 PRODUCT F-13-1 PRODU LI- O 400 K K F-6 HEAVY POLYMER 3 HEAVY POLYMER. COMMERCIAL 5 RUN F-14-1 PRODUCT CL 2 300 w I- W lOO o 20 4o 60 so 100 VOLUME *7. OVERHEAD T.B.P. DISTILLATION F I G I[ INVENTOR A TORNEYS June 1952 1.. F. BROOKE CONVERSION OF PROPYLENE POLYMERS 3 Sheets-Sheet 5 Filed June 4, 1949 LIQUID CATALYST 300 F 0-75 PSIG SOLID CATALYST 380 F 250 PSIG SPACE RATE V/V/HR.

INVENTOR L/oyofl Brooke ATTORNEYS Patented June 10, 1952 CONVERSION OF PROPYLENE POLYMERS Lloyd F. Brooke, Berkeley Highland Terrace,

Calif., assignor to California Research Corporation,.San Francisco, Calif., a corporation of Delaware Application June 4, 1949, Serial No. 97,284

3 Claims. (01. 260683.15)

This invention relates to a process for the conversion of low boiling liquid hydrocarbons produced by polymerizing propylene to higher boiling olefinic hydrocarbons by contacting said low boiling hydrocarbons with concentrated liquid phosphoric acid in the absence of propylene.

In the past, propylene has been polymerized to produce liquid hydrocarbons boiling in the gasoline range for use as motor fuel. More recently, is has been found that the higher polymers of propylene, such as the tetramer and pentamer, may be used to alkylate benzene and that the reaction product may be sulfonated to produce a detergent of superior quality. This discovery has led to the practice of commercial polymerization of propylene directed to the production of the higher propylene polymers. In typical commercial operation a, propylene containing hydrocarbon gas is polymerized by contact with a solid phosphoric acid catalyst at a temperature in the range of about 375 to 450 F. under pressure of at least 250 p. s. i. g. The reaction product is depropanized and separated into a fraction boiling below about 350 F. and a fraction boiling above about 350 E, which comprises the desired heavy propylene polymers. The lighter fraction boiling below 350 EE. is recycled to the polymerization zone, together with fresh propylene feed. In the usual practice, a recycle ratio of light polymer to propylene of 4:1 to 6:1 or higher is required in order to obtain maximum yields of the desired heavy polymer.

This process has two serious disadvantages. First, the high temperature at which it is operated is not favorable to the production of the desired heavy polymer and, accordingly, the conversion per pass is low, hence, high recycle ratios are made necessary in order to obtain an acceptable overall conversion. Second, under the conditions of temperature and recycle ratio which are employed in the process, substantial quantities of saturated hydrocarbons are produced. These saturated hydrocarbons tend to accumulate in the recycle stream, and provision must be made forv their rejection in order to permit sustained operation at reasonable conversion rates.

It is an object of this invention to efiect the conversion of the lower boiling fraction separated from the product of a propylene polymerization to higher boiling olefinic hydrocarbons at low temperatures whereby higher conversion to the heavier hydrocarbons is obtained.

It is a further object of this invention to convert the lower boiling fraction separated from the product of a propylene polymerization to higher boiling olefinic hydrocarbons without any substantial simultaneous production of saturated hydrocarbons.

In the practice of this invention the reaction product produced by catalytically polymerizing propylene is depropanized and then fractionally distilled to separate an overhead fraction boiling below about 350 F. This overhead fraction is then intimately contacted with concentrated liquid phosphoric acid at a temperature below 325 F. and usually in the range 225-325 F. to effect a substantial conversion of the overhead fraction to olefinic hydrocarbons boiling in the range 350-500 F.

The process of this invention may be better understood by reference to Figure 1 of the appended drawings, which is a diagrammatic illustration of apparatus and a process flow suitable for the practice of the invention. A feed ordinarily containing above about 20% propylene and substantially free of hydrocarbons heavier than propane is treated by conventional methods to remove hydrogen sulfide. The feed is then passed through line I into caustic washer 2,

where residual hydrogen sulfide and mercaptans are removed. The feed then is passed from caustic washer 2 through line 3 into water washer 4 and then through line 5 into drier 6, where water is removed. The feed is ordinarily dried to such a degree that its Water content is sufficient to produce a water vapor pressure approximately equal to the water vapor pressure over the solid phosphoric acid catalyst with which it is subsequently contacted. The feed then passes from drier 6 through line 1 into polymerization zone 8. Polymerizattion zone '8 is packed with solid phosphoric acid catalyst. The solid phosphoric acid catalysts are prepared by mixing liquid phosphoric acid with a siliceous adsorbent such as kieselguhr to form a paste which is then extruded, dried, calcined, and rehydrated to produce an extrudate having a dry appearance but having a substantial content of phosphoric acid. Preparation of such a catalyst is described in U. S. Patent 1,993,514. In polymerization zone 8 propylene is polymerized to form liquid polymers. The reaction product flows from polymerization zone 8 through line 9 into dust filter II], where suspended particles of the solid catalyst are removed. The feed passes from filter [0 through line H into depropanizer [2, where propane and lighter hydrocarbons are removed overhead through line 45. The depropanized reaction 3 a 4 product is withdrawn from depropanizer l2 the light polymer which is not converted in conthrough line l3 and passed into topping still I4. version zone 22 to the desired heavy product is A fraction boiling below about 350 F. is removed returned as overhead from topping still M to conoverhead through line I5 and passes through version zone 22. heat exchanger I 6, where it is cooled and con- 5 The conversion of light polymer to heavy densed, and then into reflux drum H. A portion polym r ay be practiced in the manner deof the reflux condensate is withdrawn from re- 1 scribed in'Figure 1, Where the distillation eq pfiux drum I! through line It and returned to 'mentserves both polymerization-zones or it may topping still l4 through line l9 as reflux. The, be practiced as a separate process in which light remainder of the overhead fraction boiling-'be io"p y are in from x ran us sour es low 350 F. is pumped by rpump-iorthroqghr li e and-converteditor-heavy polymer by contact with 2| into reactor 22. Reactor 22 is charged with 'th c n en r liq i phosphoric ci concentrated liquid phosphoric -acid ,-*the-concen- 7 E1161 su which y e b a by t P tration being in the range 102I1Q%*calculated ess'of the invention are illustrated by the followas orthophosphoric acid. The'hydroc'arbonsem" s mp co taining 36% by volume tering reactor 22 through line 2| and the liquid of P pyl w contacted With a Solid P phosphoric acid are intimately mixed in reactor p i 'a y at a t p tur of F. 22 by impeller 23, which is driven at arhigh rate and a pr ssu f 300 1 .5. t polymerize the of speed by motor 24 Reactor 22' is ordinarily pr pyl n The reaction p du t was deprovided with a draft tube 25, which is positioned Propanized and distilled t Separate a light p yin the reaetor' relative to-the reactor-walls and vv1111611bvelh'eadiwhich following p the impeller 23 to obtain maximum mi-xing efli- -tions:

ciencyf A rhixture ofhydrocarbon andacid is 7 f Table] V withdrawn from reactor 22- through line 26 and passed into settler 21, where the mixture .sep fififf 6 f e i p pp hydrocarbon phase and a ;fl;;-' ;g{ 1{; 118 i-lower; acid phase. The hydrocarbon phase congTBP distillation.

; in part of converted hydrocarbons boiling 0 F above -350 Fz-and in part ofunconverted feed s 50%;267o'Fr- 'Z which is subsequently separated and recycled to 30 r 0 e o '--reactor' 22." The acid phase is withdrawn-from 90% 304 95% 311 end pomtsll j "'settl'erffl through line 2'8 and returned to reactor 1 ody of'liquid phosphoric acid having a v 22, where it is fegusd; The hydrocarbon phase is concentration of'103;2%- calcula'tedas orthophoswithdrawn from 's'ettief'zi -throu h:1ine 2s and llpherieaeid Waschareed to areactorcorrespond- -ispass'ed through' one of-the two -neutralizers 30 f 0' fi 2 Of Figure 1.; The reactoremand 3|. Neutralizers 3D and 3l-are packed with 1 fployedwaslwlumnar inishape and had baflles exan alkaline material-such as lim'estone' 'and are 'walls. A stirring shaft co'nnected in parallel 7 so that one'may be on "'having'mixing e i g'from the shaft 1'? stream while the other is beingrecharged with and'lbo'sitioned Opp te the'baflles'wascentered in eamflinejmateriaL f'Th ;hyd a -bonlflows from the column; I'he clearancebetweenthe mixing the -neutralizers' 30and 31- through line 32 into blades" and :was-ap i ately e 5 inch. -iineflasnd' thence into polymertopping still [4. The-shaft retatedvat app o imately 2000 V ""Th'e-ibottoms fraction'f-rom toppingstill 14; which R. P. :M. 'during-rthe reaction. The low boiling boilsjabove'about 35d F is withdrawn from topf uct ab0ve 'described was charged to ping-still '14 through-line and is-passed'into rethe reactor and intimatelymixed'with the conrun sti11 34. -An-;overhead -fraction which boils n p or c ac d. The op ion was jfl sually in the -ra e 350=-500 is withdrawn 'conduc'ted continuously for 'a'period of'36;6 hours, 'from reruirstill fl -through1ine=-135a,nd passes duringwhich time pressure and'space velocity u exchange "36 when; t, werewaried. Theconditions of therreaction and h x tb {feiiux 1 1 531; A o t n fjhe 1 the results obtained are recorded in the following condensateis pass'e'd from reflux drum 3'l through lines and 39-into rerun-still '34 as refiux,iand 'TabZe II the' reinainder 'oi the condensate is withdrawn through line 'fimas 'the tfinal' reactiorrproduct. 7 Run Number F-13-l F-12 F-13-2 A bottoms fraction from rerun still 34* is with. l r nr .1mg 4| and asse into reboiler Hours-Operation 044 1443 14-364;

surgedruni 42. Apart'of the bottom'srproduct is g g gj g g i egg 300 300 z lr'etfi n drfromkreboflefillz ;,t l n .43 to relitratabie ciliitvI'i 'ih'lliII 99.1

'-*run*s'til1"34 and a part' of it is withdrawn from Rec I I I v I 7 ycle Ratio, Vol. Recycle/V01. Feed 0.84 1. 2.4

reborler- 42-throughline 44 'as af'product. It is }.gggzfi+groducuvohreed frequnt -v e returnvalbettomsfraetion v ii ssmsigs i ii l'fiL'Ffifii::31:I: 096i? (Phi? (Pei? w th li 44f to polymerization zone 8, Gas Pmduced None together with the fresh feed entering through 53i pe a e During the'runssummarized in the above table,

when thelprocess sco e 1n the manner 5 topping still l4, rerun 'stil1"34;"reactor 22, and j i i ly l' e in Figure 1-,; t e s 0 recycle ofthe settler 21'of' Figure 1 constituted the-entire proclower boilin -traction 0fth p p eess unit. The light polymer feed was introduced l tp p yme a Z0118 8177 iThe'entile conversion into the reactor from a storage tank rather than otth'is low boiling fraction to the'desired heavy directly from polymer topping still M, in order -polymer i's efiectedlin-reactor W re t e li that conversion rates and recycle ratios might be fractiondscontacted with concentrated-liquid accurately determined. 'It will be noted that the phosphoric acidm the absence of propylene. A *lowboiling polymer feed-to the reactor-was consmg1e=toppingstill serves tosepa'ratethe prodverted to heavier olefinicproduct-boiling" above --"ucts'ofhothpolymerization zone 8 and conversion 350 F., w yields e" e fin l. titr zonn the -fl w is such that any of ab1e aciditywas lower than the initial tit-ratable acidity as a result, mainly, of formation of phosphoric acid esters in the course of the reaction.

A steady state't itratable'acidity somewhat lower than the initial titratable acidity isordinarily established after several hours of operation. The production of very heavy polymer bottoms boiling above 500 F. was low, being on the order of and the production of saturates was very low, being below 5%. v in an amount below 5% by the process of the Production of saturates the light polymer recycle stream. In the course of saturate rejection, olefin losses are usually sustained and the overall recovery of desired polymer is thus further reduced.

At lower temperatures, saturate formation is still further reduced and at 250 F. and below, it is eliminated. This is illustrated by the following results obtained in a run at 250 F. The charge was a light propylene polymer having an API gravity of 62 and an ASTM distillation as follows: Start 121 F.; 5%146 F.; 10%153 F.; -%166 F.; %-220 R; %25 l F.; %-269 F.; %-273.5 F.; %280 F.; %-285 F.; %314 F.; %353 F.; and end point with 97.4% over-359 F. The conditions and results of the run are shown in the following Table III:

Table III Run F-47 Temp., "F 250 Pressure Atmospheric Catalyst 105.4% calculated as orthophosphoric acid v01. feed/vol. catalyst/hr 1.17

Recycle ratio, vol. re-

cycle/vol. feed 2.85 Volume 350 F.+ product/vol. feed 0.32 Volume 500 F.+ product/col. feed 0.027 Volume of saturates/vol.

feed 0.0 Gas produced None The reaction product had the following properties: A. P. I. gravity 47.6, A. S. T. M. distillation,

80%-464= F.; 90%-488 F.; 95%-506 F.; end point with 97.3% overhead 512 F.

It was further determined that if the feed rate in the run summarized in Table III were reduced'to 0.35 v./v./hr. and the other conditions were maintained constant, complete conversion of the light polymer feed to heavy polymer would be obtained.

From the runs recorded in the above tables and from further exploratory runs, it has been determined that the process may be conducted with the desired low saturate formation, low recycle rate, and high conversion at temperatures in the range 225-325 F., and preferably in the range 250-300 F. It has also been found that the concentration of the acid charged to the con- 6 "version zone should be in the range 102-110% in order to obtain the desired conversion, and that it is preferably in the range 103-107%, on the basis that the reaction proceeds satisfactorily,

that corrosion rates are lower with the more concentrated acid and that if the acid concentration is about 107%, the formation of polymers boiling above 500 F. may be undesirably increased.

The reaction may be carried out at atmospheric pressure, but a moderately elevated presssure up to 200 p. s. i. may be employed advantageously.

At superatmospheric pressures the light polymer feed may be maintained substantially completely in liquid phase, which facilitates the intimate mixing of the hydrocarbon and catalyst which is necessary toiobtain high conversions. The'space velocity should be maintained above about 0.2, since high conversions may be obtained at such space velocities and since lower space velocities result in longer contact times and tend to increase the production of undesirable saturated hydrocarbons.

In order to obtain high conversions, for example, above 70%, it is necessary that the catalyst and the hydrocarbon be subjected to very intimate mixing. It has been found that a high speed impeller mixer or, turbo mixers available commercially will prdouce the necessary degree of mixing.

While liquid phosphoric acid is known to be a polymerization catalyst, it does not appear to function primarily as a polymerization'catalyst in the process of this invention. An examination of the reaction product produced in the process of this invention indicates that the reaction the reaction product, when subjected to a true boiling point distillation, shows a uniform slope in a plot of distillation temperatures vs. per cent overhead. Such a uniform slope indicates that the hydrocarbons comprising the reaction product have varying molecular weights and that no particular molecular weight predominates in the product.

The manner in which the product of the reaction of the present invention contrasts with the products of a typical commercial polymerization reaction where recycle of the light polymer is employed is clearly shown by Figure 2 of the appended drawings. In Figure 2, the volume per 1 cent overhead is plotted against the still temperature in a true boiling point distillation.

The curves labelled F-12 Product, F-13-1 Product, and F-14-1Product," respectively, are the distillation curves for the heavy olefinic products obtained in runs F-12, F-13-1, and F-l l-l summarized in the foregoing tables. The curve 1abelled F 6, Heavy Polymer is the distillation curve for the heavy polymer produced in a run in which propylene is contacted with liquid phosphoric acid having a concentration of 103.5% calculated as orthophosphoric acid at a temperature of 300 F., a pressure of 350 p. s. i. g., and a space velocity of 0.95, and in which the light polymer product boiling below 350 F. was separated and recycled to the reaction zone together with the fresh propylene feed.

The curve labelled Heavy Polymer, Commer- .higher conversion at lower temperatures.

cia the 'distillationtfcurve of "a commercial heavy polymer obtainedzby contacting propylene with a solid phosphoric acid catalystat a temperature of 440 F., a pressure of 300-400 p. s. i. g.,

and a space velocity of 0.1 v./v./hr. In this run,

the light polymer product boiling below 350 F. was separated and recycled into contact with the solid-phosphoric acid catalyst, together-with a fresh propylene feed. During this run the recycle ratio varied between 4:1 and 6:1, that is, 4 to 6 volumes of 'light'polymer were recycled for each volumeof liquid propylene charged as fresh feed. The curves of Figure 2 indicate that the F-6 Heavy Polymer andthe Heavy Polymer, Commercial, are true polymers; Both curves show long plateaus'in which a large proportion of the total polymer distilled in a narrow temperature range,which would indicate a uniform molecular weight of the overhead obtained across the plateau; In contrast to these curves, the curves for runs F-12, F-13-1, and F-14-'-1 conducted accordin to the process of this invention show no plateaus, but, rather, a uniform slope. The curve for run F-13-1 shows a sharp rise until the first overhead has been removed, after which a uniformslope appears and persists throughout the distillation.

The productof the process of this invention characterized by uniform slope in the distillation curve as indicated in Figure 2 may be employed to considerable advantage in the preparation of alkyl aryl sulfonate detergents. When this reaction product is contacted with benzene in the presence of an alkylation catalyst under alkylation conditions and an alkylate is formed which is subsequently sulfonated to produce a detergent, the-sulfonated product will show the same variety of-molecular weights as that shown by the product of the process of the invention. The detergent thus prepared will contain hydrocarbon chains of varying lengths attached to the benzene ring. This characteristic in the detergent has been found to increase its efiiciency. A good detergent appears to have two distinct characteristics. It has the ability to wet and remove dirt from a fabric and it has the ability "to maintain the removeddirtin suspension so-that it is not reabsorbed. It appears that the short chainalkyl aryl sulfonate' detergents are more efficient in wetting the fabric and freeing the dirt from it, and that the long chain detergents are more efficient in maintaining the dirt in suspension. A detergent produced from the reaction product of the process of this invention shows both of these desirable characteristics.

It has been found that the liquid phosphoric acid here employed as the conversion catalyst is markedly superior to other polymerization catalysts which. it might be attempted to employ for the same purpose. Comparative tests havebeen made in which both liquid phosphoric acid and a solid phosphoric acid catalyst were employed as the conversion catalyst to convert lightpropylene polymer to heavier olefinic hydrocarbons in the absence of propylene. acid has been found to produce substantially In Figure 3 of the appended drawings the per cent conversion of light propylene polymer to heavy olefinic hydrocarbons boiling above 350 F. has been plotted against space rate. Two curves are The liquid phosphoric shown, one for liquid phosphoric acid at 300 F. and 0-75 -p. s. i. g., and one for solid phosphoric acid'catalyst at 380F. and 250 p. s. i. g. It is seen from the curves that the conversion'obtained with liquid phosphoric acid is somewhat more than twice the conversion obtained with the solid phosphoric acid catalyst. It' should be noted that the temperature at'which the solid phosphoric acid catalyst was employed is higher; however, this temperature was chosen because conversions obtained at lower temperatures were even less favorable.

I claim:

1. A continuous process for producing an olefinic hydrocarbon material characterizedby a 5% point above 350 F. and a point below 525 F. on a true boiling point distillation which comprises providing in a reaction zone a body of liquid phosphoric 'acid having a concentration in the range 103-110% calculated as orthophosphoric acid, intimately contactin with said acid a liquid olefinichydrocarbon fraction separated from the reaction product of a catalytic polymerization of propylene, and boiling in a range below-about 350 F., maintaining in the reaction zone a temperature below about 325 F. and contacting said hydrocarbon with said acid at a space velocity in excess of 0.2 volumes of hydrocarbon per volume of acid per hour.

2. A continuous process for the production of an olefinic hydrocarbon material having a boiling range extending substantially above 350 F. which comprises continuously introducing propylene polymers boiling below about 350 F. into a conversion zone, intimately mixing said polymers with liquid phosphoric acid having a concentration in the range 102-110% calculated as ortho-phosphoric acid in the conversion zone while maintaining therein a temperature below about 325 F., continuously withdrawing a mixture of acid and hydrocarbon from the conversion zone and settling it in a settling zone to separate an upper hydrocarbon layer and a lower acid layer, continuously returning the acid layer from the settling zone to the conversion zone and continuously withdrawing the hydrocarbon layer from the settling zone.

7 3. The method as defined in claim 2 wherein the hydrocarbon layer withdrawn from the settling zone is fractionally distilled to separate an overhead fraction boiling below about 350 F. and said overhead fraction is continuously recycled to the conversion zone.

LLOYD'F. BROOKE.

REFERENCES CITED The following references are of record in the file of this patent:

Eng. Chem., September 1935, pages 1067-1069. 

1. A CONTINUOUS PROCESS FOR PRODUCING AN OLEFINIC HYDROCARBON MATERIAL CHARACTERIZED BY A 5% POINT ABOVE 350* F. AND A 90% POINT BELOW 525* F. ON A TRUE BOILING POINT DISTILLATION WHICH COMPRISES PROVIDING IN A REACTION ZONE A BODY OF LIQUID PHOSPHORIC ACID HAVING A CONCENTRATION IN THE RANGE 103-110% CALCULATED AS ORTHOPHOSPHORIC ACID, INTIMATELY CONTACTING WITH SAID ACID A LIQUID OLEFINIC HYDROCARON FRACTION SEPARATED FROM THE REACTION PRODUCT OF A CATALYTIC 